Many women hope to keep skin fair and beautiful, and many whitening cosmetics have therefore been developed. Examples include whitening cosmetics which contain ascorbic acid or a derivative thereof, kojic acid or a derivative thereof, tranexamic acid or a derivative thereof, hydroquinone glycoside, or the like. However, most of these cosmetics have a mechanism of action in which tyrosinase and thereby biosynthesis of melanin are inhibited with limited effectiveness. That is, even though the whitening cosmetics containing these active ingredients are effective for symptoms such as age spots, freckles, and dark complexion that result from the abnormally accelerated production of melanin, such whitening cosmetics do not have much effect on dyschromatosis for which the amount of melanin produced is a lesser contributing factor. In other words, for dyschromatosis, tyrosinase inhibitors are less effective or not effective at all, and development of means for alleviating such dyschromatosis is desirable.
Examples of dyschromatosis in which melanin production is a lesser contributing factor include dyschromatosis resulting from the accelerated migration of melanin granules from melanocytic dendrites. Although it is considered that such dyschromatosis is treatable by inhibiting the elongation of dendrites that occurs when melanocytes allow melanin granules to migrate, few whitening agents utilizing such a mechanism have been known. There has been a demand for the development of whitening agents utilizing such a mechanism.
The inventors of the present invention have found that Achillea millefolium L. is a source plant for Centaureidin (5,7-dihydroxy-3,6-dimethoxy-2-(5-hydroxy-4-methoxyphenyl)-4H-1-benzopyran-4-on; hereinafter also referred to as “Compound I”) which is a compound represented by general formula (I). It was known that its extract is useful as a humectant for cosmetics (JP-A 02-172907), and in the stabilization of kojic acid in cosmetics (JP-A 07-17848). The extract inhibits tyrosinase (JP-A 08-104646), eradicates active oxygen (JP-A 11-246336), inhibits α-MSH (JP-A 11-349435), and so on. However, it was not known at all that Centaureidin inhibits the elongation of melanocytic dendrites and that it is useful for alleviating, by such action, dyschromatosis, a condition for which melanin production inhibitors with a tyrosinase inhibitory action are not completely effective.
Moreover, a compound represented by general formula (I), such as Centaureidin, was known:
1) to be found in plants of the genus Artemisia and useful for treating allergic diseases (published international application WO 20020419109);
2) to have anti-cancer action (U.S. Pat. No. 493,540); and
3) to be found in plants of the genus Centaurea cyanus (Flamini Guido et. al., Phytochemistry, 58 (8), 1229-1233, 2001).
However, it was not known at all that such a substance is present in Achillea millefolium L. of the family Asteraceaeis. It was not known in the least that this substance inhibits the elongation of melanocytic dendrites, and that it is useful for alleviating, by such action, dyschromatosis for which melanin production inhibitors with tyrosinase inhibitory action are not completely effective.